Eszopiclone and dexmedetomidine depress ventilation in obese rats with features of metabolic syndrome

Effect of dexmedetomidine on cardiorespiratory regulation in spontaneously breathing adult rats

Purpose

We examined the cardiorespiratory effect of dexmedetomidine, an α2- adrenoceptor/imidazoline 1 (I1) receptor agonist, in spontaneously breathing adult rats.

Methods

Male rats (226−301 g, n = 49) under isoflurane anesthesia had their tail vein cannulated for drug administration and their tail artery cannulated for analysis of mean arterial pressure (MAP), pulse rate (PR), and arterial blood gases (PaO2, PaCO2, pH). After recovery, one set of rats received normal saline for control recording and was then divided into three experimental groups, two receiving dexmedetomidine (5 or 50 μg·kg−1) and one receiving normal saline (n = 7 per group). Another set of rats was divided into four groups receiving dexmedetomidine (50 μg·kg−1) followed 5 min later by 0.5 or 1 mg∙kg−1 atipamezole (selective α2-adrenoceptor antagonist) or efaroxan (α2-adrenoceptor/I1 receptor antagonist) (n = 6 or 8 per group). Recordings were performed 15 min after normal saline or dexmedetomidine administration.

Results

Compared with normal saline, dexmedetomidine (5 and 50 μg·kg−1) decreased respiratory frequency (fR, p = 0.04 and < 0.01, respectively), PR (both p < 0.01), and PaO2 (p = 0.04 and < 0.01), and increased tidal volume (both p = 0.049). Dexmedetomidine at 5 μg·kg−1 did not significantly change minute ventilation (V′E) (p = 0.87) or MAP (p = 0.24), whereas dexmedetomidine at 50 μg·kg−1 significantly decreased V′E (p = 0.03) and increased MAP (p < 0.01). Only dexmedetomidine at 50 μg·kg−1 increased PaCO2 (p < 0.01). Dexmedetomidine (5 and 50 μg·kg−1) significantly increased blood glucose (p < 0.01), and dexmedetomidine at 50 μg·kg−1 increased hemoglobin (p = 0.04). Supplemental atipamezole or efaroxan administration similarly prevented the 50 μg·kg−1 dexmedetomidine-related cardiorespiratory changes.

Principal conclusion

These results suggest that dexmedetomidine-related hypoventilation and hypertension are observed simultaneously and occur predominantly through activation of α2-adrenoceptors, but not I1 receptors, in spontaneously breathing adult rats.

Comparison of clinical efficacy and safety between dexmedetomidine and propofol among patients undergoing gastrointestinal endoscopy: a meta-analysis

OBJECTIVE

To compare the clinical efficacy and safety of dexmedetomidine and propofol in patients who underwent gastrointestinal endoscopy.

METHODS

Relevant studies comparing dexmedetomidine and propofol among patients who underwent gastrointestinal endoscopy were retrieved from databases such as PubMed, Embase, and Cochrane Library.

RESULTS

Seven relevant studies (dexmedetomidine group, n = 238; propofol group, n = 239) met the inclusion criteria. There were no significant differences in the induction time (weighted mean difference [WMD] = 3.46, 95% confidence interval [CI] = -0.95-7.88, I2 = 99%) and recovery time (WMD = 2.74, 95% CI = -2.72-8.19, I2 = 98%). Subgroup analysis revealed no significant differences in the risks of hypotension (risk ratio [RR] = 0.56, 95% CI = 0.25-1.22) and nausea and vomiting (RR = 1.00, 95% CI = 0.46-2.22) between the drugs, whereas dexmedetomidine carried a lower risk of hypoxia (RR = 0.26, 95% CI = 0.11-0.63) and higher risk of bradycardia (RR = 3.01, 95% CI = 1.38-6.54).

CONCLUSIONS

Dexmedetomidine had similar efficacy and safety profiles as propofol in patients undergoing gastrointestinal endoscopy.

Dexmedetomidine Improves Cardiovascular and Ventilatory Outcomes in Critically Ill Patients: Basic and Clinical Approaches

Dexmedetomidine (DEX) is a highly selective α2-adrenergic agonist with sedative and analgesic properties, with minimal respiratory effects. It is used as a sedative in the intensive care unit and the operating room. The opioid-sparing effect and the absence of respiratory effects make dexmedetomidine an attractive adjuvant drug for anesthesia in obese patients who are at an increased risk for postoperative respiratory complications. The pharmacodynamic effects on the cardiovascular system are known; however the mechanisms that induce cardioprotection are still under study. Regarding the pharmacokinetics properties, this drug is extensively metabolized in the liver by the uridine diphosphate glucuronosyltransferases. It has a relatively high hepatic extraction ratio, and therefore, its metabolism is dependent on liver blood flow. This review shows, from a basic clinical approach, the evidence supporting the use of dexmedetomidine in different settings, from its use in animal models of ischemia-reperfusion, and cardioprotective signaling pathways. In addition, pharmacokinetics and pharmacodynamics studies in obese subjects and the management of patients subjected to mechanical ventilation are described. Moreover, the clinical efficacy of delirium incidence in patients with indication of non-invasive ventilation is shown. Finally, the available evidence from DEX is described by a group of Chilean pharmacologists and clinicians who have worked for more than 10 years on DEX.

Buprenorphine Depresses Respiratory Variability in Obese Mice with Altered Leptin Signaling

BACKGROUND

Opiate-induced respiratory depression is sexually dimorphic and associated with increased risk among the obese. The mechanisms underlying these associations are unknown. The present study evaluated the two-tailed hypothesis that sex, leptin status, and obesity modulate buprenorphine-induced changes in breathing.

METHODS

Mice (n = 40 male and 40 female) comprising four congenic lines that differ in leptin signaling and body weight were injected with saline and buprenorphine (0.3 mg/kg). Whole-body plethysmography was used to quantify the effects on minute ventilation. The data were evaluated using three-way analysis of variance, regression, and Poincaré analyses.

RESULTS

Relative to B6 mice with normal leptin, buprenorphine decreased minute ventilation in mice with diet-induced obesity (37.2%; P < 0.0001), ob/ob mice that lack leptin (62.6%; P < 0.0001), and db/db mice with dysfunctional leptin receptors (65.9%; P < 0.0001). Poincaré analyses showed that buprenorphine caused a significant (P < 0.0001) collapse in minute ventilation variability that was greatest in mice with leptin dysfunction. There was no significant effect of sex or body weight on minute ventilation.

CONCLUSIONS

The results support the interpretation that leptin status but not body weight or sex contributed to the buprenorphine-induced decrease in minute ventilation. Poincaré plots illustrate that the buprenorphine-induced decrease in minute ventilation variability was greatest in mice with impaired leptin signaling. This is relevant because normal respiratory variability is essential for martialing a compensatory response to ventilatory challenges imposed by disease, obesity, and surgical stress.

Assessment of dexmedetomidine effects on left ventricular function using pressure-volume loops in rats

PURPOSE

The role of dexmedetomidine on left ventricular function is ambiguous. We analyzed pressure-volume loops to investigate whether dexmedetomidine has a myocardial depressive effect.

METHODS

Thirty-two Sprague-Dawley rats were anesthetized and a pressure-volume loop catheter was advanced into the left ventricle. Rats were divided into four groups (n = 8 each). The control group received a 10-min infusion of 0.1 ml of normal saline, and the other three groups received 1.0 (Dex1.0 group) , 2.5 (Dex2.5 group), and 5.0 μg/kg (Dex5.0 group) dexmedetomidine in a similar fashion to the control group. Steady-state hemodynamic parameters were recorded. The inferior vena cava was occluded intermittently to assess preload-independent indices.

RESULTS

Compared with the control group, changes in the Dex1.0 group were insignificant. In the Dex2.5 group, only the systolic blood pressure was higher (vs control, P = 0.03), and other parameters were insignificant. The Dex5.0 group exhibited a lower heart rate, higher systolic blood pressure, higher arterial elastance (vs control, all P < 0.001), and unaltered cardiac output. The Dex5.0 group showed steeper slopes of end-systolic pressure increment and end-systolic pressure-volume relationship than the control, Dex1.0, and Dex2.5 groups (all P < 0.001). Slopes of end-diastolic pressure decrement and end-diastolic pressure-volume relationship did not differ among groups.

CONCLUSION

Dexmedetomidine had no direct myocardial depressant effect in the rat heart in doses that are similar to those encountered under clinical conditions. Dexmedetomidine did not significantly alter the ability of the heart to cope with bradycardia and greatly increased afterload. Their potentially negative impact on cardiac output was effectively attenuated by improved myocardial contractility and preserved diastolic function in healthy subjects.

Dexmedetomidine post-treatment induces neuroprotection via activation of extracellular signal-regulated kinase in rats with subarachnoid haemorrhage

BACKGROUND

Dexmedetomidine, a sedative agent, provides neuroprotection when administered during or before brain ischaemia. This study was designed to determine whether dexmedetomidine post-treatment induces neuroprotection against subarachnoid haemorrhage (SAH) and the mechanisms for this effect.

METHODS

Subarachnoid haemorrhage was induced by endovascular perforation to the junction of the right middle and anterior cerebral arteries in adult rats. Dexmedetomidine was applied immediately or 2 h after onset of SAH. Neurological outcome was evaluated 2 days after SAH. Right frontal cortex area 1 was harvested 24 h after SAH for western blotting.

RESULTS

Subarachnoid haemorrhage reduced neurological scores and increased brain oedema and blood-brain barrier permeability. These effects were attenuated by dexmedetomidine post-treatment. Neuroprotection by dexmedetomidine was abolished by PD98095, an inhibitor of extracellular signal-regulated kinase (ERK) activation. Phospho-ERK, the activated form of ERK, was increased by dexmedetomidine; this activation was inhibited by PD98095.

CONCLUSIONS

Dexmedetomidine post-treatment provides neuroprotection against SAH. This effect appears to be mediated by ERK.

Dexmedetomidine-induced sedation does not mimic the neurobehavioral phenotypes of sleep in Sprague Dawley rat

STUDY OBJECTIVES

Dexmedetomidine is used clinically to induce states of sedation that have been described as homologous to nonrapid eye movement (NREM) sleep. A better understanding of the similarities and differences between NREM sleep and dexmedetomidine-induced sedation is essential for efforts to clarify the relationship between these two states. This study tested the hypothesis that dexmedetomidine-induced sedation is homologous to sleep.

DESIGN

This study used between-groups and within-groups designs.

SETTING

University of Michigan.

PARTICIPANTS

Adult male Sprague Dawley rats (n = 40).

INTERVENTIONS

Independent variables were administration of dexmedetomidine and saline or Ringer's solution (control). Dependent variables included time spent in states of wakefulness, sleep, and sedation, electroencephalographic (EEG) power, adenosine levels in the substantia innominata (SI), and activation of pCREB and c-Fos in sleep related forebrain regions.

MEASUREMENTS AND RESULTS

Dexmedetomidine significantly decreased time spent in wakefulness (-49%), increased duration of sedation (1995%), increased EEG delta power (546%), and eliminated the rapid eye movement (REM) phase of sleep for 16 h. Sedation was followed by a rebound increase in NREM and REM sleep. Systemically administered dexmedetomidine significantly decreased (-39%) SI adenosine levels. Dialysis delivery of dexmedetomidine into SI did not decrease adenosine level. Systemic delivery of dexmedetomidine did not alter c-Fos or pCREB expression in the horizontal diagonal band, or ventrolateral, median, and medial preoptic areas of the hypothalamus.

CONCLUSIONS

Dexmedetomidine significantly altered normal sleep phenotypes, and the dexmedetomidine-induced state did not compensate for sleep need. Thus, in the Sprague Dawley rat, dexmedetomidine-induced sedation is characterized by behavioral, electrographic, and immunohistochemical phenotypes that are distinctly different from similar measures obtained during sleep.

Effects of dexmedetomidine on cardiorespiratory regulation in spontaneously breathing newborn rats

BACKGROUND

Dexmedetomidine, a selective α2-adrenoceptor agonist, is a new sedative agent.

OBJECTIVE

To examine the dexmedetomidine-associated changes in cardiorespiratory indices in spontaneously breathing newborn rats.

METHODS

An abdominal catheter to administer drugs and subcutaneous electrodes to record electrocardiographic data were inserted into 2- to 4-day-old rats under isoflurane anesthesia; the rats were then placed in individual chambers. After recovery from the anesthesia, the rats received intraperitoneal administrations of normal saline (NS, vehicle), dexmedetomidine (50 μg·kg(-1)), or dexmedetomidine (50 μg·kg(-1)) followed 5 min later with NS or the selective α2-adrenoceptor antagonist atipamezole (1 mg·kg(-1)) (n = 10 in each group). Cardiorespiratory indices were recorded for each animal throughout the experiment.

RESULTS

Dexmedetomidine administration significantly decreased heart rate (HR) and minute ventilation (V'E) (P < 0.05) compared with control, whereas NS administration did not. The decrease in HR and V'E after dexmedetomidine administration was significantly less in rats that received atipamezole (P < 0.05) than in those that received NS after dexmedetomidine administration. The dexmedetomidine-associated V'E depression was attributed to a significant decrease in respiratory frequency (fR) but not tidal volume (VT ). The change in fR was reversed by atipamezole administration, which itself induced no significant changes in HR and fR.

CONCLUSION

In spontaneously breathing immature rats, dexmedetomidine administration significantly reduced HR and V'E. Because atipamezole fully reversed decreases in fR and therefore V'E, dexmedetomidine-related respiratory suppression occurs predominantly through α2-adrenoceptor-related suppression of fR.